UPPER MIOCENE BEDS. 39 



anticline they are continuously exposed, with only a break where 

 the Irrawaddi crosses them, from the Themathank Chaung, at the 

 south-east corner of block 50 N of the Yenangyaung oil-field, 

 seven miles south of Singu, to the farthest limit of my survey, which 

 is twenty-eight miles to the north of Singu, and the exposure 

 probably extends some distance beyond. The sandstones are mostly 

 fine-grained, soft, and yellow, brown, grey or white in colour. The 

 shales are greyish or greenish and are likewise mostly quite soft. 

 Between the sandstones and the shales there is every gradation, and 

 rocks composed of alternate thin layers of shale and sandstone are 

 quite common. In both sandstones and shales there are hard 

 calcareous bands strings and nodules, which are greyish in colour. 

 These nodules are often of considerable size and are commonly 

 three or four feet across, mammilated or kidney-shaped, and when 

 weathered they break along the original planes of bedding. These 

 nodules and pieces of the bands are everywhere found lying on 

 the surface of the ground, and the slopes of the hills are covered 

 with them. Subordinate bands of conglomerate too are found in 

 several places, but they are never of any great thickness, nor are the 

 pebbles of large size, and some of the calcareous bands contain rounded 

 pebbles of limestone derived from other beds. The beds of shale 

 and clay, and in places the uppermost sandstone, contain numerous 

 flakes of gypsum scattered through them, the quantity of which 

 varies greatly in different localities, but it is never entirely absent, 

 and its presence is one of the distinguishing characteristics of the 

 shales of the Yenangyaung stage. In the shales, and occasionally in 

 the sandstones, there are also nodules of marcasite, which in the days 

 of the Burmese kings were collected and used in the manufacture of 

 gunpowder, and in some of the lower beds one finds calcite crystal- 

 lized in the crevices. 



All my attempts to subdivide the upper miocene beds by their 

 lithological characters were without success, as they change very 

 rapidly, both in thickness and character along the strike, and it is 



( 39 ) 



